Meanwhile back of topic ...
If Pargyle is correct, and I have no reason to believe otherwise, we're looking at a maximum temperature gradient between inside and outside at the top of a 14x12 hive of 10 degrees. Putting 10cm of EPF on the top reduces heat losses through the crown board but this still leaves the walls where heat can be lost.
The temperature under the crown board is the same as the temperature at the top of the wall and 11cm height of wall perimeter has the same area as the roof so you could lose nearly as much heat through the top of the walls as you lose through the roof.
The temperature inside the hive at the OMF is the same as the outside temperature so this reduces the temperature gradient across the hive walls as you descend down the walls, so you lose less heat but nevertheless I suspect you lose another "roofsworth" of heat energy in the rest of the wall, below the 11cm mark - my calculus is not up to doing the calculations!
To mind simple mind, it makes sense to insulate the walls as well as the roof, with the walls losing twice as much heat, in total, as the roof.
It also makes sense to try to shed any water falling on the roof so that you're not losing latent heat of vapourisation. Keeping the hive/insulation as dry as possible seems to me to be desireable.
I know there are lots of people out there who will disagree with my analysis but I will care for my bees according to what I think the best solution is. Others might get good results using other methods - I might get Hawklord's honey crop quantity next year if only I can master swarm control. That's the problem with beekeeping - there are so many variables that when you think you've mastered on aspect, another come along and stings you on the bottom.
CVB
